1. Field of the Invention
The present invention relates to a non-impact printer, and more particularly to a printer improved in printing quality to provide a natural printing image for a curve, a slash or the like.
2. Description of the Prior Art
Hitherto, in a non-impact printer such as an electrophotographic printer, an electrically charged photoconductor drum is illuminated with a light source to form an electrostatic latent image on a surface thereof, a developing is performed upon adhesion of a toner to the electrostatic latent image, to form a toner image, and then the thus obtained toner image is transferred to a recording material to be fixed thereon.
FIG. 2 is a block diagram of a printer control circuit for use in a conventional non-impact printer. In the figure, a printing control unit 1 transmits, at the time point that a sheet arrives at a printing ready point, a timing signal 12, including a line and a raster timing signal, to a host or another controller, and receives video data 11 which has been edited on each page in a host or another controller. The received video data 11 in the printing control unit 1 is transmitted to an LED (Light Emitting Diode) head 19 in the form of a real printing data signal 18. Upon receipt of a line of video data 11, the control unit 1 transmits a latch signal 17 to the LED head 19 so as to hold the real printing data signal 18 therein. Before receiving the subsequent data from a host or another controller, the thus held real printing data signal 18 is visualized in print when the print head 19 receives a printing drive signal 13. The real printing data signal 18 is transmitted to the LED head 19 in synchronism with a clock signal 18a. 
Transmission and receipt operation of the video data 11 is performed in the unit of print lines. FIG. 3 is an operational time chart of the conventional non-impact printer as mentioned above.
However, according to the conventional non-impact printer as mentioned above, the printing is performed in accordance with image data or video data 11 transmitted from the host controller as it is, or depending on resolution of the LED head 19 which is determined by an arrangement of the LED devices at regular intervals in a raster direction. Thus, there will be retained a serrated edge-like image on a slash portion of the printed image due to the resolution.
It is therefore an object of the present invention, in view of the foregoing problems, to provide an improved printer.
It is another object of the present invention to provide a non-impact printer capable of printing with a resolution higher than that of video data received from another controller or a host controller.
It is still another object of the present invention to provide a non-impact printer capable of reducing a serrated edge-like image on a slash portion of the printed image, thereby improving a printing quality.
In accordance with a preferred embodiment of the present invention, there is disclosed a non-impact printer provided with control means for providing a sequence control for the printer in its entirety in response to a control signal and a video data from another controller, comprising: means for generating line timing signals for printing on basic raster lines, and additional line timing signals each for printing on a sub-raster line during an interval of basic raster lines; line buffer means adapted for storing the received video datas in units of lines at predetermined continuous-line correspondence; means responsive to the line timing signals for causing the video data to be sequentially stored in said line buffer means; logical operation circuit means for taking out the video data stored in said line buffer in units of columns, performing a logical operation for the obtained video data in accordance with function groups each previously defined, and outputting a first correction output data for printing on the basic raster line and at least one second correction output data for printing on the sub-raster line; and means for transmitting the first and second correction output data to a print head in the form of a real printing data signal in synchronism with the line timing signal and the additional line timing signal, respectively; wherein said control means includes means for setting a print head drive energy for printing on the basic raster lines and a print head drive energy for printing on the additional raster lines independently of each other.
In accordance with another preferred embodiment of the invention, there is disclosed a non-impact printer provided with control means for providing a sequence control for the printer in its entirety in response to a control signal and a video signal from another controller, comprising: means for generating line timing signals for printing on basic raster lines, and additional line timing signals each for printing on a sub-raster line during an interval of a receiving timing of the line timing signals; line buffer means adapted for storing the received video data in units of lines at predetermined continuous-line correspondence; means responsive to the line timing signals for causing the video data to be sequentially stored in said line buffer means; means for taking out the video data stored in said line buffer in units of dots, and performing a logical operation for location of the center of gravity of the peripheral dots in the center the obtained dot; and a table conversion logical operation circuit for converting location information obtained by the logical operation into the corresponding output patterns, and transmitting the thus obtained output patterns to a print head in the form of a real printing data signal in synchronism with the line timing signal and the additional line timing signal, respectively; wherein said control means includes means for setting a print head drive energy for printing on the basic raster lines and a print head drive energy for printing on the additional raster lines independently of each other.